#include <stdio.h>
#include <stdlib.h>


	int fuction(int num)
{
	int n = 0;
	if(num == 2 || num == 1)
		return 1;
	return fuction(num-1) + fuction(num-2);
}





	int main()
{
	int num;
	int ret;
	scanf("%d",&num);
		
	ret = fuction(num);
	printf("%d\n",ret);
	exit(1);
}
